A specific material that detergent formulators wish to include in a laundry detergent liquid composition is HEDP (1-hydroxyethane 1,1-diphosphonic acid), preferably as a sodium salt, and sold under the trade name Dequest 2010 by Thermphos. HEDP is known in laundry formulations as a sequestrant/chelating agent to control Ca2+, Mg2+ levels and to sequestrate metal ions which helps to remove certain types of troublesome stains such as red wine, tea etc. If HEDP could be included at concentration of at least 2 weight %, a small dose of non-aqueous liquid delivered from a water soluble capsule would give significant benefits on such stains. However, this 2 weight % level far exceeds the solubility of HEDP in conventional non-aqueous liquid. Even if the levels of solvent in the liquid were increased, the inclusion of HEDP at the required effective level into such non-aqueous liquids remains a problem because it does not stay in solution over time. It is also undesirable to increase non-aqueous solvent or hydrotrope levels to solve the problem in this way.
A further problem facing laundry detergent manufactures, especially when powders are employed, is the deposition of un-dissolved residues formed from components of the detergent formulation remaining on the laundry when the wash is complete. This is a particular problem when washing dark laundry as residues remaining on the laundry wash appear as white powdery dustings, or even worse, as white jelly like deposits, which cannot simply be brushed away by the consumer. This is most undesirable for consumers and the environment as significant levels of ‘fines’ require the laundry to be re-washed, using additional water and power to complete the laundry task.
The term ‘fines’ refers to a granular fraction present in for example HEDP and which may arise from a breakdown of the compound during manufacture and processing.
Therefore, a problem remains for the detergent formulators of how to incorporate the desired level of HEDP in a laundry detergent formulation, in combination with other laundry components, without obtaining residual deposits on the washed laundry.
U.S. Pat. No. 6,815,410 (P&G) suggests to agglomerate the HEDP and suspend it in the liquid. Suspension requires some form of liquid structuring and the resulting liquid is cloudy. Consumers prefer clear liquids. Suspended materials also need to be well dispersed during manufacturing or else the concentration levels within the formulation vary undesirably from one capsule to another, with consequent variable performance and reduced stability. HEDP is also known to sometimes have adverse reactions with other laundry ingredients, especially certain enzymes, which are usually present in non-aqueous laundry liquids in capsules. In EP1319707 (Unilever) there is taught the phase separation of solid and liquid parts within a capsule. It has, however, been found that consumers do not appreciate such a phase separated approach. An alternative approach is described in EP1328616 (P&G) where selected insoluble benefit agents are suspended in the liquid inside the capsule by use of an additional external structuring system. Like solvents and hydrotropes, such a structuring system adds volume, cost and complexity to the capsule and some otherwise suitable structuring systems may provide further limitations on the types of ingredients that may be incorporated into the liquid. For example the hydrogenated castor oil taught in EP1328616 is incompatible with lipolytic enzyme inclusion.
Consequently, the problem of how to include a desired amount of HEDP in a laundry detergent formulation has been reconsidered. It is well known to use separate compartments within a capsule to segregate ingredients. Multi-compartment capsules having stacked, internally divided or side by side compartments have been described in the patent literature. Segregation by means of one compartment inside another compartment is known from EP1293557 (Unilever).
In addition, in WO2010/088112, a two-compartment “stacked” capsule is disclosed having a smaller liquid compartment and a larger powder compartment. The two compartments are separated by a layer of polyvinylalcohol film. This disclosure is mainly focused on dishwashing compositions. The exemplary two compartment capsule has a powder compartment mainly composed of percarbonate bleach granules. HEDP is included in the powder at a level of 1.5 weight % of the total composition. The liquid compartment has an undesirably high level of non-aqueous solvent level at over 60 weight % of the total composition and it contains no enzymes.
WO2001/083657 (P&G) discloses a multi-compartment pouch made from a water-soluble film and having at least two compartments, wherein a least one compartment comprises a solid component of a composition and at least one compartment comprises a liquid component of a composition. Materials normally supplied as granules and insoluble materials, for example surfactants, insoluble builders and enzymes are described as such solid components. Examples are given of laundry detergent compositions in a polyvinyl alcohol pouch. The materials disclosed in this patent document for inclusion in the “solid compartment” evolve gas on contact with water. It is believed that the gas evolved from such materials counters the ingress of water through a rupture hole in the capsule film and allows the film to continue to dissolve from the outside before the solid contents dissolve to form a strong enough electrolytic solution inside the capsule compartment to significantly inhibit further film dissolution. Inclusion of a non-gas generating material like HEDP into a solid compartment without a significant amount of gas evolving material also in the solid compartment poses problems. Furthermore, as HEDP has interactions with enzymes, this configuration of HEDP and enzymes in the same compartment is not desirable.
A multi-compartment capsule is also disclosed in EP 1375637 and EP 1394065 (Unilever). These publications disclose multi-compartment packages comprising between 2 to 5 compartments and obtained by thermoforming a water-soluble film. Each compartment of the package contains a different part of a cleaning composition and the compartments are connected to each other and separated from one another by at least one flat seal area. One compartment may contain a liquid part of the detergent composition and another compartment a granular part of the composition, for example: bleach or builder.
Incomplete dissolution of polyvinylalcohol capsules when placed in a wash cycle may also lead to some residue deposition formed from the capsule material. Furthermore, incomplete dissolution of the capsules may also lead to entrapment of powder components, and thereby exacerbate the problem of unsightly residues being deposited on the washed laundry.
None of the above prior art documents address the issue of residue deposition when using HEDP in a laundry formulation, and none of the prior art documents detail how such problems may be mitigated.
There therefore exists the need for a multi-compartment water soluble laundry detergent capsule which is able to deliver the required level of HEDP in a laundry formulation and which overcomes the problems of prior art capsules.
In addition, there exists the need for a multi-compartment water soluble laundry detergent capsule which is able to deliver the required level of HEDP in a laundry formulation and which provides acceptable wash capabilities, with greatly reduced or no deposition of component residue or capsule on the laundry.
Surprisingly, the inventors have now found that controlling the level of certain fractions of fine material, commonly referred to as ‘fines’, present in the HEDP has a profound effect on the deposition of residues arising from either the polyvinyl alcohol film or the components of the laundry composition.